Isolation work station

ABSTRACT

An isolation work station comprising an enclosure, and an air circulation system and high efficiency air filter for generating a downwardly directed laminar air flow through the enclosure. Periodic sterilization of the enclosure may be accomplished by adding a sterilant, such as vaporized hydrogen peroxide, to the airstream, and the filter is impregnated with a catalyst for degrading the vaporized hydrogen peroxide during the purge cycle and wherein the airstream is circulated at a relatively low speed so as to increase the residence time in the filter.

BACKGROUND OF THE INVENTION

The present invention relates to an isolation work station suitable forproviding an ultra clean work environment for the production of sterileproducts, drug manufacturing operations, and the like.

Work station isolators are known which comprise a generally rectangularenclosure having a glass front wall which mounts one or two flexiblegloves for permitting a technician to reach through the wall and intothe enclosure to perform work tasks therein and while being isolatedfrom the environment within the enclosure. Also, in order to minimizethe chances for contamination, isolators of this type commonly provide afiltered, laminar air flow downwardly through the enclosure, so as toprevent airborne contaminants from coming into contact with the sterileproducts being processed in the enclosure.

In the case of many manufacturing or assembly operations, it isnecessary to completely sterilize the interior of the isolator betweenmanufacturing operations, so as to prevent product contamination. As oneexample, the Food and Drug Administration (FDA) currently recommendsthat all medical and surgical products be sterilized so as to achieve alive organism count of less than one part per million in the enclosure.In order to provide such sterilization, steam or ethylene oxidetreatments have been suggested, but more conventionally, thesterilization is accomplished by vaporized hydrogen peroxide which iscirculated through the enclosure for a period of time, such as 10-15minutes. A generator capable of generating vaporized hydrogen peroxidefor this purpose is disclosed, for example, in U.S. Pat. Nos. 4,863,688and 4,935,371, and such a generator is manufactured by the AmericanSterilizer Company of Erie, Pa. as Model No. VHP1000.

After sterilization is complete, it is necessary to then flush theresidual hydrogen peroxide from the isolator, and this is typicallyaccomplished by passing an airstream through the isolator while bleedingoff a parallel stream which is passed through a granular gas type filterwhich contains a catalyst for degrading the residual hydrogen peroxideinto moisture and oxygen, and which is located in the vaporized hydrogenperoxide generator. Since the hydrogen peroxide is absorbed by plastic,and other materials which are normally present in the isolator, it takesa significant time, typically 24 hours, for these materials to offgasthe hydrogen peroxide and for the isolator to reach the required levelsto permit the isolator to be reused with other products.

It is an object of the present invention to provide a work stationisolator of the described type which has the capability of rapidly andefficiently purging the residual hydrogen peroxide from the isolatorafter the sterilization procedure.

It is a further object of the present invention to provide an isolationwork station of the described type which, during the normal cycle ofoperation, efficiently degrades any residual hydrogen peroxide which maybe released from the components of the work station after the purgingcycle is completed.

SUMMARY OF THE INVENTION

The above and other objects and advantages of the present invention areachieved by the provision of an isolation work station which comprises agenerally rectangular enclosure comprising upstanding front and rearside walls, and upstanding opposite end walls, and with the side wallsand the end walls defining an open top and an open bottom of theenclosure. Upper and lower plenums communicate with the open top andopen bottom of the enclosure respectively, and at least one highefficiency particulate air filter is sealably mounted in the upperplenum and so as to be disposed horizontally across substantially theentire area of the top of said enclosure. Also, the filter includes asterilant degrading catalyst.

At least one flexible glove is sealably mounted in the front side wallof the enclosure, which is transparent, so as to permit a technician toreach through the front side wall and into the enclosure to perform worktasks therein and while being isolated from the environment within theenclosure. Also, an air circulation system is provided for circulatingair downwardly through the filter and the enclosure and comprising amain duct extending from the lower plenum to the upper plenum at alocation above the filter, and a blower positioned in the main duct forcausing air to flow through the main duct from the lower plenum to theupper plenum and then through the filter and the enclosure and back tothe lower plenum.

The isolation work station of the present invention preferably alsocomprises an air inlet duct communicating with the outside environmentand with the main duct, and a first valve positioned in the air inletduct for permitting selective flow therethrough. Further, a first portis provided which communicates with the main duct for permitting themain duct to be selectively connected to the inlet of a generator ofvaporized sterilant, such as hydrogen peroxide, and second port isprovided which communicates with the main duct at a location downstreamof the first port for permitting the main duct to be selectivelyconnected to the outlet of the vaporized sterilant generator.

The work station of the present invention preferably also comprises asecondary duct connected to the main duct at a location which isdownstream of the second port and which communicates with the upperplenum or the enclosure at a location below the filter. A second valveis provided for permitting selective flow through the secondary duct. Bythis arrangement, an airstream containing the vaporized sterilant may bedelivered into the enclosure of the work station and so as to circulatethrough the enclosure and thereby contact and bio-decontaminate surfaceswithin the enclosure.

In the preferred embodiment of the present invention, the filtercomprises a sheet of high efficiency or "absolute" filtering media whichis folded in accordion fashion upon itself to form a filter pack, andthe filter media is coated or impregnated with a catalyst which rapidlydegrades the sterilant during the sterilant purging cycle. Also, thecatalyst bearing filter serves to protect the products within theenclosure from any offgasing sterilant which is released from thematerials in the isolator after the isolator has been purged and againstarted to run in its normal operating cycle. Where the sterilant ishydrogen peroxide, the catalyst preferably comprises titanium oxide,which promotes the degradation of hydrogen peroxide into water vapor andoxygen, and which is generated by a smoke bomb of the typeconventionally used to charge high efficiency air filters with smokeduring a leak testing procedure. Thus the filter media can be coated orimpregnated with titanium oxide by the same process presently employedfor charging the media during a leak testing procedure. Other catalystsare known which promote the degradation of hydrogen peroxide, and othermethods to coat or impregnate the filter media could be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects and advantages of the present invention having beenstated, others will appear as the description proceeds, when taken inconjunction with the accompanying drawings, in which

FIG. 1 is a perspective view of an isolation work station which embodiesthe present invention, and which illustrates the manner in which worktasks are performed by the technician while remaining isolated from theinterior of the work station;

FIG. 2 is a schematic sectional view of the work station illustrated inFIG. 1;

FIGS. 3-5 are schematic perspective views of the work station andparticularly illustrating the air circulation system of the work stationduring normal operation, pressure decay testing, and sterilizationcycles, respectively; and

FIG. 6 is a view similar to FIG. 2 but illustrating a second embodimentof the work station.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate an isolation work station 10 which embodies thepresent invention, and which comprises a generally rectangular enclosure12 which includes upstanding front and rear side walls, 13, 14, andupstanding opposite end walls, 15, 16, with the side walls and end wallsdefining an open top and an open bottom of the enclosure. As best seenin FIG. 1, the end wall 16 includes a product entry port 18 ofconventional design, and the front and rear walls 13, 14 comprisetransparent glass and the front wall sealably mounts a pair of flexiblegloves 20 in the conventional manner, and so as to permit a technicianto reach through the front side wall and into the enclosure to performwork tasks therein, and while being isolated from the environment withinthe enclosure.

An upper plenum 21 communicates with the open top of the enclosure 12,and a lower plenum 22 communicates with the open bottom of theenclosure. A high efficiency particulate air filter 24 is sealablymounted in the upper plenum, and so as to be disposed horizontallyacross substantially the entire area of the top of the enclosure. Inaccordance with industry standards, the high efficiency particulate airfilter 24, also commonly referred to as an "absolute" filter, comprisesa rectangular frame 25 having a centrally disposed air flow openingtherethrough, and a filter pack 26 sealably mounted in the frame andfilling the airflow opening. The filter pack 26 comprises a sheet offiltering media folded upon itself in accordion fashion, and with thefiltering media being capable of removing at least 99.9% of thesubmicron sized particles from the air passing therethrough. Filters ofthe described type are further described in U.S. Pat. Nos. 4,584,005 and4,030,518, the disclosures of which are expressly incorporated herein byreference. Also, in accordance with the present invention, the filtermedia is impregnated with a catalyst, such as an oxide of titanium, inthe manner and for the purposes further described below.

In the illustrated embodiment, a conventional light fixture 27 ismounted in the upper plenum 21 immediately above each of the front andrear end walls 13, 14. Also, the open bottom of the enclosure 12 mountsa perforated floor plate 28, which supports the products being processedin the enclosure while permitting air flow vertically therethrough andinto the lower plenum 22.

The isolation work station 10 further comprises an air circulationsystem for circulating air downwardly through the filter and theenclosure in a laminar flow pattern. The air circulation systemcomprises a main duct 30 extending from the lower plenum 22 to the upperplenum 21 at a location above the filter 24, and a blower 31 ispositioned in the main duct 30 for causing air to flow through the mainduct from the lower plenum to the upper plenum and then through thefilter 24 and enclosure 12 and back to the lower plenum.

An air inlet duct 32 communicates with the outside environment and withthe main duct 30, and a first control valve CV-1 is positioned in theair inlet duct for permitting selective flow therethrough. Also, a highefficiency particulate air filter 34 is positioned in the air inlet duct32 downstream of the valve CV-1.

In order to permit the air circulation system to be operativelyconnected to a sterilant generator 36 of the type described above, thereis provided a first port 37 in the main duct for connecting to the inletof the generator, and a second port 38 connected to the air inlet duct32 for selectively connecting the main duct to the outlet of thegenerator 36. In the preferred embodiment, the generator 36 generates anairstream containing vaporized hydrogen peroxide, and may, for example,comprise the known unit manufactured by American Sterilizer Company asdescribed above.

The air circulation system further includes a secondary duct 40connected to the main duct 30 at a location which is downstream of theconnection with the air inlet duct 32, and which communicates with theend wall 15 of the enclosure at a location below the filter 24. A secondcontrol valve CV-2 is provided in the secondary duct 40 for permittingselective flow therethrough. Also, the secondary duct 40 is preferablyoriented with respect to the enclosure so as to enter the enclosure justabove the floor plate 28 and in an inclined direction as seen in FIG. 5,so as to form a vortex which circulates through the enclosure andthereby contacts and sterilizes all surfaces within the enclosure.

The main duct 30 further defines a main duct segment 42 which extendsfrom the location at which the secondary duct 40 connects to the mainduct 30 and to the upper plenum 21. Also, a third control valve CV-3 ispositioned in the main duct segment for permitting selective flowtherethrough.

FIG. 3 illustrates the confirmation of the isolation work station inboth its normal operation cycle and its purge cycle as described below.During these cycles, valves CV-1 and CV-3 are open, and valve CV-2 isclosed. The blower 31 is operated at a speed so as to generate acirculating air flow as illustrated. The fact that the valve CV-1 isopen serves to equalize pressure differences resulting from movements ofthe gloves 20 in the enclosure 12, and normally an insignificant flowenters or leaves through the air inlet duct 32 during these cycles.

FIG. 4 illustrates the configuration during the pressure decay cycle,which differs from the cycle of FIG. 1 in that the valve CV-1 is closed.The system is thus closed to the atmosphere, and the system is thenoperated with a positive air pressure so that any leaks in the systemmay be detected by a pressure drop occurring within the system.

FIG. 5 illustrates the configuration during the sterilization cycle. Inthis cycle, a sterilant generator as described above is connected to thefirst and second ports 37, 38. The valve CV-1 is closed, and the valvesCV-2 and CV-3 are alternately opened and closed in an opposite sequence.More particularly, when the valve CV-2 is open, the valve CV-3 isclosed, and the sterilant bearing airstream is directed directly intothe enclosure so as to sterilize the surfaces and products therein.Also, in the illustrated embodiment, the secondary duct 40 is orientedso as to direct the airstream into the enclosure in a circular pattern,which creates a vortex within the enclosure which facilitates contactand sterilization of all surfaces. When the valve CV-3 is open and thevalve CV-2 is closed, the sterilant bearing airstream passes through thefilter 24 and into the enclosure 12.

Preferably, during the sterilization cycle, the blower speed isincreased to about twice its speed during normal operation so that theairstream has a sufficiently short residence time in the filter 24 topreclude significant degradation of the sterilant by the catalyst in thefilter.

When sterilization is completed, which typically takes 10-15 minutes,the work station is reconfigured to the mode of FIG. 3, and the purgingoperation is commenced. All of the air is then circulated through thecatalyst bearing filter 24, in this case at a relatively slow speed soas to increase the residence time of the sterilant in the filter. As aresult, the catalyst is able to quickly degrade the sterilant intoharmless byproducts, such as moisture and oxygen in the case of hydrogenperoxide sterilant. Such purging typically requires 10-15 minutes.

Once normal operation has commenced, it will be understood that the aircontinues to circulate through the filter 24, which acts to degrade anyresidual sterilant which is subsequently released by the materials inthe enclosure.

As a specific example, the enclosure 12 has a horizontal cross sectionalarea of about 4.5 square feet, and during the normal operation andpurging cycles (FIG. 3), the blower 31 is operated at a speed so as todeliver approximately 100 cfpm through the enclosure, and during thesterilization cycle (FIG. 5), the blower 31 is operated to deliverapproximately 200 cfpm through the enclosure.

As indicated above, the filter 24 preferably comprises a sheet offiltering media folded in accordion fashion to form a filter pack 26. Inaccordance with the present invention, it has been found that the filtermay be readily impregnated with a hydrogen peroxide degrading catalyst,by impregnating the media with the smoke of a conventional smoke bomb ofthe type used to charge a high efficiency air filter during a leak testprocedure. As a specific example, the filter 24 in the upper plenum 21of the work station as described above may have a size of 18×36×57/8thinches, and a conventional smoke bomb stick is broken in an airstream sothat the generated smoke passes through the filter. A suitable smokebomb stick of this type is manufactured by E. Vernon Hill Incorporated,of Benicia, Calif., and each such stick contains approximately two ml(0.07 fl. oz.) of titanium tetrachloride (TiCl₄) in a sealed glass vial.TiCl₄ combines with atmospheric moisture to form hydrochloric acid (HCL)along with titanium oxychloride and titanium dioxide. These componentsare collected on the filtering media, and it is believed that theTitanium dioxide acts as a catalyst for degrading the vaporized hydrogenperoxide which is subsequently passed through the filter into moistureand oxygen.

FIG. 6 illustrates a second embodiment of an isolation work station inaccordance with the present invention. In this embodiment, the upperplenum mounts a second high efficiency particulate air filter 24Aparallel to and below the catalyst bearing filter 24. The second filter24A, however, is free of the sterilant degrading catalyst. Also, thesecondary duct 40 communicates with the upper plenum at a locationbetween the catalytic filter 24 and the second conventional filter 24A.

In the embodiment of FIG. 6, the valve CV-3 is open during the normaland purge cycles, so that the airstream passes downwardly through bothfilters. During sterilization, the valve CV-3 is closed and the valveCV-2 is open, as illustrated, whereby the sterilant bearing airstreampasses only through the second filter 24A. Thus the sterilant bearingairstream does not pass through the catalyst in the upper filter 24, andany degradation of the sterilant in the upper filter is thereby avoided.

In the drawings and the specification, there has been set forthpreferred embodiments of the invention and, although specific terms areemployed, the terms are used in a generic and descriptive sense only andnot for the purpose of limitation, the scope of the invention being setforth in the following claims.

What is claimed is:
 1. An isolation work station suitable for providingan ultra clean work environment for the production of sterile products,drug manufacturing operations, and the like, and comprising:a generallyrectangular enclosure comprising upstanding front and rear side walls,and upstanding opposite end walls, with said side walls and said endwalls defining an open top and an open bottom of said enclosure, saidfront side wall of said enclosure being transparent, and said enclosurefurther comprising at least one flexible glove sealably mounted in saidfront side wall of said enclosure so as to permit a technician to reachthrough said front side wall and into the enclosure to perform worktasks therein and while being isolated from the environment within theenclosure, upper and lower plenums communicating with the open top andopen bottom of the enclosure respectively, filtering means comprising atleast one high efficiency particulate air filter sealably mounted insaid upper plenum and so as to be disposed horizontally acrosssubstantially the entire area of the top of said enclosure, and withsaid filtering means including a sterilant degrading catalyst, and anair circulation system for circulating air downwardly through saidfiltering means and said enclosure and comprising a main duct extendingfrom said lower plenum to said upper plenum at a location above saidfiltering means, and a blower positioned in said main duct for causingair to flow through said main duct from said lower plenum to said upperplenum and then through said filtering means and said enclosure and backto said lower plenum, an air inlet duct communicating with the outsideenvironment and with said main duct, and first valve means positioned insaid air inlet duct for permitting selective flow therethrough, firstport means communicating with said main duct for permitting the mainduct to be selectively connected to the inlet of a vaporized sterilantgenerator, and second port means communicating with the main duct at alocation downstream of said first port means for permitting the mainduct to be selectively connected to the outlet of the vaporizedsterilant generator.
 2. The isolation work station as defined in claim 1further comprising a secondary duct connected to said main duct at alocation which is downstream of said second port means and whichcommunicates with said upper plenum or said enclosure at a locationbelow said filtering means, and second valve means in said secondaryduct for permitting selective flow therethrough.
 3. The isolation workstation as defined in claim 2 wherein said main duct includes a mainduct segment which extends between said location at which the secondaryduct connects to said main duct and said upper plenum, and third valvemeans in said main duct segment for permitting selective flowtherethrough.
 4. The isolation work station as defined in claim 2wherein said one filter comprises a sheet of filtering media folded inaccordion fashion upon itself to form a filter pack, with said filteringmedia being impregnated with the sterilant degrading catalyst, and aframe sealably surrounding and supporting the filter pack.
 5. Theisolation work station as defined in claim 4 wherein the sterilantdegrading catalyst comprises an oxide of titanium.
 6. The isolation workstation as defined in claim 4 wherein said upper plenum mounts a secondhigh efficiency particulate air filter parallel to and below said onefilter, with said second filter being free of said sterilant degradingcatalyst, and wherein said secondary duct communicates with said upperplenum at a location between said one filter and said second filter. 7.The isolation work station as defined in claim 6 wherein said secondfilter comprises a sheet of filtering media folded in accordion fashionupon itself to form a filter pack, and a frame sealably surrounding andsupporting the filter pack.
 8. An isolation work station suitable forproviding an ultra clean work environment for the production of sterileproducts, drug manufacturing operations, and the like, and comprising:agenerally rectangular enclosure comprising upstanding front and rearside walls, and upstanding opposite end walls, with said side walls andsaid end walls defining an open top and an open bottom of saidenclosure, upper and lower plenums communicating with the open top andopen bottom of the enclosure respectively, filtering means comprising atleast one high efficiency particulate air filter sealably mounted insaid upper plenum and so as to be disposed horizontally acrosssubstantially the entire area of the top of said enclosure, at least oneflexible glove sealably mounted in said front side wall of saidenclosure so as to permit a technician to reach through said front sidewall and into the enclosure to perform work tasks therein and whilebeing isolated from the environment within the enclosure, an aircirculation system for circulating air downwardly through said filteringmeans and said enclosure and comprising a main duct extending from saidlower plenum to said upper plenum at a location above said filteringmeans, and a blower positioned in said main duct for causing air to flowthrough said main duct from said lower plenum to said upper plenum andthen through said filtering means and said enclosure and back to saidlower plenum, an air inlet duct communicating with the outsideenvironment and with said main duct, and first valve means positioned insaid air inlet duct for permitting selective flow therethrough,vaporized sterilant generator means including an inlet line and anoutlet line through which a vaporized sterilant is delivered, first portmeans for permitting the main duct to be selectively connected to theinlet line of said vaporized sterilant generator means, second portmeans communicating with the main duct at a location downstream of saidfirst port means for permitting the main duct to be selectivelyconnected to the outlet line of said vaporized sterilant generatormeans, and said filtering means including a catalyst which degrades thesterilant generated by said generator.
 9. The isolation work station asdefined in claim 8 wherein said one filter comprises a sheet offiltering media folded in accordion fashion upon itself to form a filterpack, with said filtering media being impregnated with said catalyst,and a frame sealably surrounding and supporting the filter pack.
 10. Theisolation work station as defined in claim 9 wherein said vaporizedsterilant generator means acts to generate vaporized hydrogen peroxide,and wherein said catalyst comprises an oxide of titanium.
 11. Theisolation work station as defined in claim 9 further comprising asecondary duct connected to said main duct at a location which isdownstream of said second port means and which communicates with saidupper plenum or said enclosure at a location below said filtering means,and second valve means in said secondary duct for permitting selectiveflow therethrough.
 12. The isolation work station as defined in claim 11wherein said main duct includes a main duct segment which extendsbetween said location at which the secondary duct connects to said mainduct and said upper plenum, and third valve means in said main ductsegment for permitting selective flow therethrough.
 13. An isolationwork station suitable for providing an ultra clean work environment forthe production of sterile products, drug manufacturing operations, andthe like, and comprising:a generally rectangular enclosure comprisingupstanding front and rear side walls, and upstanding opposite end walls,with said side walls and said end walls defining an open top and an openbottom of said enclosure, said front side wall of said enclosure beingtransparent, and said enclosure further comprising at least one flexibleglove sealably mounted in said front side wall of said enclosure so asto permit a technician to reach through said front side wall and intothe enclosure to perform work tasks therein and while being isolatedfrom the environment within the enclosure, upper and lower plenumscommunicating with the open top and open bottom of the enclosurerespectively, first filtering means comprising at least one air filtersealably mounted in said upper plenum, and with said first filteringmeans including a sterilant degrading catalyst, second filtering meanscomprising at least one air filter scalably mounted in said upper plenumdownstream of said first filtering means, with said second filteringmeans being free of said sterilant degrading catalyst, and an aircirculation system for circulating air downwardly through said first andsecond filtering means and said enclosure and comprising a main ductextending from said lower plenum to said upper plenum at a locationupstream of said first filtering means, a blower positioned in said mainduct for causing air to flow through said main duct from said lowerplenum to said upper plenum and then through said first and secondfiltering means and said enclosure and back to said lower plenum, and asecondary duct connected to said main duct and communicating with saidupper plenum at a location between said first and second filteringmeans, and valve means in said secondary duct for permitting selectiveflow therethrough.
 14. The isolation work station as defined in claim 13wherein said main duct includes a main duct segment which extendsbetween the location at which the secondary duct connects to said mainduct and said upper plenum, and valve means in said main duct segmentfor permitting selective flow therethrough.
 15. The isolation workstation as defined in claim 14 further comprising an air inlet ductcommunicating with the outside environment and with said main duct, andvalve means positioned in said air inlet duct for permitting selectiveflow therethrough.
 16. The isolation work station as defined in claim 15further comprising first port means communicating with said main ductfor permitting the main duct to be selectively connected to the inlet ofa vaporized sterilant generator, andsecond port means communicating withthe main duct at a location downstream of said first port means forpermitting the main duct to be selectively connected to the outlet ofthe vaporized sterilant generator.
 17. The isolation work station asdefined in claim 16 wherein the secondary duct is connected to said mainduct at a location which is downstream of said second port means. 18.The isolation work station as defined in claim 13 wherein said firstfiltering means comprises a sheet of high efficiency particulate airfiltering media folded in accordion fashion upon itself to form a filterpack, with said filtering media being impregnated with the sterilantdegrading catalyst, and a frame sealably surrounding and supporting thefilter pack, and second filtering means comprises a sheet of highefficiency particulate air filtering media folded in accordion fashionupon itself to form a filter pack, and a frame sealably surrounding andsupporting the filter pack of the second filter.
 19. The isolation workstation as defined in claim 14 wherein the sterilant degrading catalystcomprises an oxide of titanium.